The ES78 module is an excellent inter-patch VCA, featuring very low noise and exponential response. It was designed as a small VCA function for use at various places within a system for internal VCA functions (as opposed to the VCA's for output mixing).
The ES78 has an audio taper that is an exponential curve with a 12db per volt sensitivity throughout the range except below about 0.5 volts. Below this threshold, the output of the VCA will decrease rapidly to completely attenuate the signal. This response is perfect for our envelope voltage range, and is responsible for exceptionally quiet operation.
Control voltage rejection is very high, and the unit cannot be overdriven beyond a gain factor of two.